Semiconductor device with adhesion-improvement capacitor and process for producing the device

ABSTRACT

A semiconductor device equipped with information storage capacitor comprising a first capacitor electrode, an oxide film, a second capacitor electrode and insulating films containing silicon as a main constituting element, wherein at least one of first and second capacitor electrodes contains as a main constituting element at least one element selected from rhodium, ruthenium, iridium, osmium and platinum, and as an adding element at least one element selected from palladium, nickel, cobalt and titanium, is excellent in adhesiveness between the capacitor electrodes and the insulating films.

BACKGROUND OF THE INVENTION

This invention relates to a semiconductor device, particularly to asemiconductor device equipped with a capacitor for storing informationexcellent in adhesiveness between a capacitor electrode film and aninsulating film.

With recent miniaturization of semiconductor devices, there is atendency to reduce the area of a capacitor for storing information. Andit is likely for the value of capacity to decrease. The capacity C inthe case of, e.g. a parallel plate electrode structure is determined bythe formula: C=∈·S/d, wherein ∈ is a dielectric constant, S is an areaof electrode, and d is a thickness of dielectric (a distance betweenelectrodes). In order to secure the capacity without increasing the areaof electrode S used in the capacitor for storing information, it isnecessary to reduce the film thickness d of dielectric. At present, thefilm thickness of capacitor dielectric films (insulating films) isreduced to about 10 nm. In the case of integrated memories of 64 M bitor more, thinness of the capacitor dielectric films is becoming to alimit. For this reason, materials for capacitor dielectric films havinghigher dielectric constant ∈ are being developed now. For example, inthe case of 64 to 256 M bit, the use of tantalum oxide (Ta₂O₅) isstudied, and JP-A 9-186299 discloses the use of barium strontiumtitanate (Ba_(x)SrTi_(s)O_(t): BST), etc. for 1 G bid DRAM. Further, asnon-volatile memories, JP-A 10-189881 discloses the use of leadzirconate titanate (Pb_(x)Zr_(y)Ti_(s)O_(t): PZT), etc.

It is known that these oxide films such as BST and PZT do not exhibitgood properties unless subjected to high temperature treatment, such asas high as about 600° C. or higher. Thus, as the capacitor. electrodematerials contacting with the oxide film such as BST, PZT, etc., it isnecessary to use a material which is hardly oxidized at hightemperatures. This is because when the capacitor electrode is made of amaterial easily oxidized, oxidation reaction takes place at a contactsinterface between the electrode and. the oxide film at high temperaturesto deteriorate properties of the oxide film. From the above-mentionedbackground, there have been studied as hardly oxidized capacitorelectrode materials noble metals such as rhodium (Rh), ruthenium (Ru),iridium (Ir), osmium (Os), platinum (Pt), etc., and electroconductiveoxides such as ruthenium oxide (Ru_(x)O_(y)) and iridium oxide(Ir_(x)O_(y)), etc.

It is known that oxide films such as BST and PZT do not exhibit goodproperties unless subjected to high temperature treatment as mentionedabove. And in order to use for DRAM having 1 G bit or more, it becomesto know that sufficient properties are not exhibited unless subjected tohigh temperature treatment in an oxygen atmosphere. Thus, in theproduction of DRAM having 1 G bit or more, it is necessary to conduct ahigh temperature treatment at about 600° C. or higher in an oxygenatmosphere. But, noble metals such as ruthenium which is studied as theelectrode material have poor adhesion to silicon oxide (SiO₂) used as aninsulating film, and show a problem of adhesive fracture when subjectedto high temperature treatment particularly in oxygen atmosphere.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semiconductordevice improved in adhesiveness between capacitor electrodes formed byusing as a principal material a noble metal such as ruthenium, platinum,or the like, or an electroconductive oxide such as ruthenium oxide,iridium oxide, or the like and an insulating film containing silicon.Another object of the present invention is to provide a semiconductordevice having higher reliability. A further object of the presentinvention is to provide a semiconductor device having enhanced yield inthe production thereof. The present invention still further provides aprocess for producing these semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the main part of the semiconductordevice of Example 1.

FIG. 2 is a plan view showing plane layout of the semiconductor deviceof Example 1.

FIG. 3 is a graph showing dependency of adhesive fracture energy betweenan electrode film and silicon oxide film on palladium concentration whenpalladium is added as the adding element to the electrode filmcomprising rhodium, ruthenium and platinum.

FIG. 4 is a graph showing dependency of adhesive fracture energy betweenan electrode film and silicon oxide film on titanium concentration whentitanium is added as the adding element to the electrode film comprisingrhodium, ruthenium and platinum.

FIG. 5 is a graph showing dependency of adhesive fracture energy betweenan electrode film and silicon oxide film on the bonding energy betweenthe added element and silicon when the concentration of added element isset at 20 atom %.

FIG. 6 is a drawing showing atomic configuration at an equilibrium statewhen simulation of formation of ruthenium capacitor electrode containing25 atom % of titanium on SiO₂ is conducted.

FIG. 7 is a drawing showing atomic configuration at an equilibrium statewhen simulation of formation of ruthenium capacitor electrode containing25 atom % of zirconium on SiO₂ is conducted.

FIG. 8 is a drawing showing atomic configuration at an equilibrium statewhen simulation of formation of ruthenium capacitor electrode containing26 atom % of titanium on SiO₂ is conducted.

FIG. 9 is a cross-section view showing production step for the main partof the semiconductor device of Example 1.

FIG. 10 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 1.

FIG. 11 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 1.

FIG. 12 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 1.

FIG. 13 is a cross-sectional view showing the main part of thesemiconductor device of Example 2.

FIG. 14 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 2.

FIG. 15 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 2.

FIG. 16 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 2.

FIG. 17 is a cross-section view showing production step for the mainpart of the semiconductor device of Example 2.

FIG. 18 is a cross-sectional view showing major portions for the mainpart device of Example 3.

FIG. 19 is a cross-sectional view showing the main part of thesemiconductor device of Example 4.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have earnestly studied improvement in adhesivenessbetween the capacitor electrode and the insulating film, and as aresult, we have found the following things. First, as a cause of lowadhesiveness between a capacitor electrode formed by a noble metal suchas ruthenium, or an electroconductive oxide such as ruthenium oxide(hereinafter referred to as “capacitor electrode material”) and siliconoxide film (insulating film), it was found that bond between thecapacitor electrode material and the silicon, that is, bond energybetween the capacitor electrode material and the silicon is too small.It was also found that in order to improve the adhesiveness, it iseffective to add an element having a larger bond energy with siliconthan the bond energy between the capacitor electrode material and thecapacitor electrode material.

It was also found that it is important for the adding element to havethe following factors. One of the factors is that when the bond energybetween the adding element and the silicon is about 2 times or more aslarge as the bond energy between the capacitor electrode material andthe silicon, it is possible to obtain necessary adhesiveness. That is,the adding element should have the bond energy with silicon which is 2times as large as the bond energy between the capacitor electrodematerial and silicon.

Other factors relate to the following facts found by the presentinventors mentioned below. According to the study of the presentinventors, it is important not to cause disturbance undesirable foratomic configuration of the capacitor electrode material due to theadding element in the capacitor electrode film formed by the capacitorelectrode material containing the adding element. For such a purpose, itis desirable that the atomic radius of the adding element is more closeto that of the capacitor electrode material. In practice, the atomicradius of the adding element is required to have the value of 10% orless of that of the capacitor electrode material.

As the adding element satisfying the above-mentioned factors, there canbe used palladium(Pd), nickel (Ni), cobalt (Co), titanium (Ti), etc.When ruthenium is used as the main constituting element of the capacitorelectrode, the most preferable adding element is titanium and nickel.

The adding amount of the adding element to the capacitor electrode is,according to the present inventors' study, as follows. When the addingamount is over about 10 atom % (atomic percent), the adhesive fractureenergy between the capacitor electrode and the silicon oxide filmsuddenly increases. When the adding amount is about 15 atom %, theadhesive fracture energy becomes almost constant. A critical amount ofthe adding amount of adding element is about 25 atom %. When the addingamount is over the critical value, the atomic configuration of thecapacitor electrode material disturbs undesirably. Thus, the addingamount of the adding element is preferably about 10 atom % to about 25atom %.

Embodiments of the present invention are as follows.

(1) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode and second capacitor electrode, said first capacitor electrodeor said second capacitor electrode containing as a main constitutingelement at least one element selected from the group consisting ofrhodium, ruthenium, iridium, osmium, and platinum, and as an addingelement at least one element selected from the group consisting ofpalladium, nickel, cobalt, and titanium.

(2) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode and second capacitor electrode, said first capacitor electrodeor said second capacitor electrode containing as a main constitutingelement ruthenium, and as an adding element at least one elementselected from the group consisting of palladium, nickel, cobalt, andtitanium.

(3) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the firstcapacitor.electrode and second capacitor electrode, said first capacitorelectrode or said second capacitor electrode containing as a mainconstituting element ruthenium, and as an adding element titanium.

(4) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode and second capacitor electrode, said first capacitor electrodeor said second capacitor electrode containing as a main constitutingelement ruthenium, and as an adding element nickel.

(5) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an, insulating film containing silicon as a mainconstituting element and formed in-contact with the first capacitorelectrode and second capacitor electrode, said first capacitor electrodeor said second capacitor electrode containing as a main constitutingmaterial, at least one material selected from ruthenium oxide andiridium oxide, and as an adding element at least one element selectedfrom the group consisting of palladium, nickel, cobalt, and titanium.

(6) A semiconductor device described in above (1) to (5), wherein theadding element is contained in a concentration of 10 to 25 atom %.

(7) A semiconductor device equipped with a capacitor for storinginformation comprising an oxide film for a dielectric formed between afirst capacitor electrode and a second capacitor electrode, and aninsulating film containing silicon as a main constituting element beingformed for insulating the first capacitor electrode and the secondcapacitor electrode, wherein an electroconductive film containing as amain constituting element at least one element selected from the groupconsisting of palladium, nickel, cobalt and titanium is formed betweenthe first capacitor electrode or the second capacitor electrode and theinsulating film, and the first capacitor electrode or the secondcapacitor electrode is formed from at least one element selected fromthe group consisting of rhodium, ruthenium, iridium, osmium and platinumas a main constituting element.

(8) A semiconductor device equipped with a capacitor for storinginformation comprising an oxide film for a dielectric formed between afirst capacitor electrode and a second capacitor electrode, and aninsulating film containing silicon as a main constituting element beingformed for insulating the first capacitor electrode and the secondcapacitor electrode, wherein an electroconductive film containing as amain constituting element at least one element selected from the groupconsisting of palladium, nickel, cobalt and titanium is formed betweenthe first capacitor electrode or the second capacitor electrode and theinsulating film, and the first capacitor electrode or the secondcapacitor electrode is formed from ruthenium as a main constitutingelement.

(9) A semiconductor device equipped with a capacitor for storinginformation comprising an oxide film for a dielectric formed between afirst capacitor electrode and a second capacitor electrode, and aninsulating film containing silicon as a main constituting element beingformed for insulating the first capacitor electrode and the secondcapacitor electrode, wherein an electroconductive film containing as amain constituting element titanium is formed between the first capacitorelectrode or the second capacitor electrode and the insulating film, andthe first capacitor electrode or the second capacitor electrode isformed from ruthenium as a main constituting element.

(10) A semiconductor device equipped with a capacitor for storinginformation comprising an oxide film for a dielectric formed between afirst capacitor electrode and a second capacitor electrode, and aninsulating film containing silicon as a main constituting element beingformed for insulating the first capacitor electrode and the secondcapacitor electrode, wherein an electroconductive film containing as amain constituting element at least one element selected from the groupconsisting of palladium, nickel, cobalt and titanium is formed betweenthe first capacitor electrode or the second capacitor electrode and theinsulating film, and the first capacitor electrode or the secondcapacitor electrode is formed from at least one material selected fromthe group consisting of ruthenium oxide and iridium oxide as a mainconstituting material.

(11) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode and second capacitor electrode, wherein said first capacitorelectrode or said second capacitor electrode is formed from a pluralityof electrode films, and an electrode film among the plurality ofelectrode films contacting with the insulating film contains as a mainconstituting element at least one element selected from the groupconsisting of rhodium, ruthenium, iridium, osmium, and platinum, and asan adding element at least one element selected from the groupconsisting of palladium, nickel, cobalt, and titanium.

(12) A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode and second capacitor electrode, wherein said first capacitorelectrode or said second capacitor electrode is formed from a pluralityof electrode films, and an electrode film among the plurality ofelectrode films contacting with the insulating film contains as a mainconstituting material at least one material selected from the groupconsisting of ruthenium oxide and iridium oxide, and as an addingelement at least one element selected from the group consisting ofpalladium, nickel, cobalt, and titanium.

(13) A semiconductor device described in above (11) or (12), wherein theadding element is contained in a concentration of 10 to 25 atom %.

(14) A process for producing a semiconductor device equipped with acapacitor for storing information comprising a substrate, a firstcapacitor electrode formed on the substrate, an oxide film formed incontact with the first capacitor electrode, a second capacitor electrodeformed in contact with the oxide film, and an insulating film containingsilicon as a main constituting element and formed in contact with thefirst capacitor electrode and second capacitor electrode, whichcomprises forming at least one of the first capacitor electrode and thesecond capacitor electrode by using

(a) at least one element selected from the group consisting of rhodium,ruthenium, iridium, osmium and platinum as a main constituting element,or

(b) at least one material selected from the group consisting ofruthenium oxide and iridium oxide as a main constituting material, andat least one element selected from the group consisting of palladium,nickel, cobalt, and titanium as an adding element.

(15) A process for producing a semiconductor device equipped with acapacitor for storing information comprising an oxide film formedbetween a first capacitor electrode and a second capacitor electrode,and an insulating film containing silicon as a main constituting elementbeing formed for insulating the first capacitor electrode and the secondcapacitor electrode, which comprises

forming an electroconductive film containing as a main constitutingelement at least one element selected from the group consisting ofpalladium, nickel, cobalt and titanium between the first capacitorelectrode or the second capacitor electrode and the insulating film.

The present invention is illustrated by way of the following Examples,but needless to say, it is not limited thereto.

EXAMPLE 1

The semiconductor device of this example takes a form of DRAM (dynamicrandom access memory). FIG. 1 is a cross-sectional view of the memorycell of DRAM and FIG. 2 is a part of plane layout of DRAM. FIG. is across-sectional view on line A-B or C-D of FIG. 2. As shown in FIG. 1,the semiconductor device (DRAM) equips a MOS (metal oxide semiconductor)transistors 2 formed on active regions of a main surface of a siliconsubstrate 1, and capacitor 3 for storing information positioned at upperportion of the transistors 2. These elements are arranged in parallel inthe plane direction and separated by each insulating film 4.

The MOS transistors 2 for memory cell selection comprises a gateelectrode 5, a gate insulating film 6, and diffusion layers 7 and 8. Thegate insulating film 6 is made from, for example, a silicon oxide film,silicon nitride film or a ferroelectric substance film or a laminatethereof. The gate electrode 5 is made from, for example, apolycrystalline silicon film, a metal thin film or a metal silicide filmor a laminate thereof. On upper portion and side walls of the gateelectrode 5, an insulating film 9 made from, e.g. a silicon oxide film,is formed. One of diffusion layer 7 of the MOS transistor 2 is connectedto a bit line 11 via a plug 10. Upper portion of the MOS transistor 2 iscovered with an insulating film 12 a for interlaminar insulation such asa BPSG (boron-doped phosphosilicate glass) film, a SOG (spin on glass)film, a silicon oxide film or silicon nitride film formed by a CVD(chemical vapor deposition) method or a sputtering method.

On the insulating film 12 a covering the MOS transistor 2, capacitor 3for storing information are formed, and an insulating film 12 b madefrom, e.g., a silicon oxide film, is formed for interlaminar insulation.The information storing capacitor 3 is connected to a diffusion layer 8at another side of the MOS transistor 2 via, for example, a plug 13 madeof polycrystalline silicon. The information storing capacitor acomprises an electroconductive barrier layer 14, a first capacitorelectrode 15, a dielectric oxide film 16 having high dielectric constantor ferroelectricity and a second capacitor electrode 17 from the bottomin a laminated structure. The upper portion thereof is covered with aninsulating film 18 made from a silicon oxide film for interlaminarinsulation.

In the above mentioned structure of the device, one feature of thepresent invention is in that either one or both of the first capacitorelectrode 15. and the second capacitor electrode 17 are formed by (i) atleast one element selected from the group consisting of rhodium (Rh),ruthenium (Ru), iridium (Ir), osmium (Os) and platinum (Pt) as a mainconstituting element or (ii) at least one material selected from thegroup consisting of ruthenium oxide (Ru_(x)O_(y)) and iridium oxide.(Ir_(x)O_(y)) as a main constituting material and at least one elementselected from the group consisting of palladium (Pd), nickel (Ni), andtitanium (Ti) as an adding element in an amount of 10 atom % to 25 atom%. The term “main constituting element” means an element which iscontained in the largest amount, and the term “main constitutingmaterial” means a material which is contained in the largest amount.

By making the special element the main constituting element, or makingthe special material the main constituting material and containing thespecial adding element in a predetermined amount, the adhesiveness ofthe first capacitor electrode 15 and the second capacitor electrode 17to the insulating film 12 b and the insulating film 18 can be enhancedremarkably. This is explained in detail below.

The present inventors examined how the adhesive fracture energy betweenthe capacitor electrode film and the insulating film changes by theadding element contained in the capacitor electrode film using moleculardynamic simulation. The molecular dynamic simulation is a method, asdisclosed in Journal of Applied Physics, vol. 54, pages 4864-4878, 1983,comprising calculating forces acting on individual atoms throughpotentials among atoms, and solving the Newton's equation of motionbased on the obtained forces to calculate the positions of individualatoms at each time. The adhesive fracture energy U means an energynecessary for causing adhesive fracture between the capacitor electrodefilm and the insulating film. This is explained, for example, inInternational Journal of Fracture, vol. 66, pages 45-70, 1994. In thepresent case, the value U was calculated by subtracting a total ofinteratomic potentials inside of both systems of the capacitor electrodefilm and the interlaminar insulating film from a total of interatomicpotentials inside of the capacitor electrode film plus a total ofinteratomic potentials inside of the interlaminar insulation film.

As one example, FIG. 3 is a graph showing changes of the adhesivefracture energy against palladium concentrations in the case ofsimulation wherein a film (capacitor electrode film) containing as amain component rhodium, ruthenium and platinum, respectively, andpalladium is formed on a SiO₂ film at 900 K and cooled to 300 K. Theordinate axis of the graph is standardized by the adhesive fractureenergy U_(Ru) for the ruthenium film containing no adding element andthe ruthenium film. The film thickness was 3 nm for both the capacitorelectrode film and the SiO₂ film. The adhesive fracture energy means theenergy necessary for causing adhesive fracture between the capacitorelectrode film and the silicon oxide (SiO₂) film. It is clear from FIG.3 that when the palladium concentration becomes about 10 atom % or more,the adhesive fracture energy increases abruptly to remarkably improvethe adhesiveness between the capacitor electrode film and the siliconoxide (SiO₂) film.

Similarly, FIG. 4 shows changes of adhesive fracture energy against thetitanium concentration in the case of making the capacitor electrodefilm using rhodium, ruthenium or platinum as a main constituting elementand titanium. As is clear from FIG. 4, when the concentration of addingelement of titanium becomes about 10 atom % or more, the adhesivefracture energy increases abruptly to remarkably improve theadhesiveness between the capacitor electrode film and the silicon oxidefilm. From FIGS. 3 and 4, it becomes clear that when the concentrationof adding element becomes about 10 atom %, the adhesive fracture energyincreases abruptly to remarkably improve the adhesiveness, but when theconcentration of the adding element becomes more than about 15 atom %,almost constant adhesive fracture energy is obtained to mean that theeffect for improving adhesiveness is saturated.

Next, which kinds of adding elements improve the adhesiveness with thesilicon oxide film was analyzed. As the adding element, palladium,cobalt, nickel, titanium, hafnium (Hf), zirconium (Zr) and phosphorus(P) in adding concentration of 20 atom % was examined. Adhesive fractureenergy of ruthenium electrode film containing an adding element andplatinum electrode film against the silicon oxide film, respectively,was examined and at the same time the relation of each adding element tobond energy to silicon was also examined. The results are shown in FIG.5, wherein the ratio of E/E_(B-S1) is taken along the abscissa axis andthe adhesive fracture energy of the electrode film to the silicon oxidefilm is taken along the ordinate axis. In the above, E means bond energybetween an adding element and silicon, and E_(B-S1) means bond energybetween the main constituting element in the electrode film (rutheniumor platinum) and silicon. As shown in FIG. 5, it is understood that whenthe bond energy of the adding element to silicon is 2 times or more aslarge as the bond energy between the main constituting element of thecapacitor electrode film and silicon, the adhesiveness between thecapacitor electrode film and the silicon oxide film is particularlyimproved. Concretely, palladium, cobalt, nickel, titanium, hafnium andzirconium are effective for improving the adhesiveness.

The kind of adding element effective for improving the adhesivenessbecomes clear as mentioned above. Another problem is when these addingelements are contained in the electrode film, if the formation ofperovskite crystal structure of the oxide film material dielectric suchas BST, PZT, etc. becomes impossible on the electrode film due todisturbance of atomic arrangement in the electrode film, exhibition of afunction of BST, PZT, etc. as ferroelectric substance or high dielectricsubstance becomes impossible. Thus, a molecular dynamic simulation forspecifying an adding element which does not disturb atomic arrangementof the electrode film was conducted.

FIG. 6 is a drawing showing atomic arrangement or configuration inequilibrium state when simulation was conducted by forming a capacitorelectrode film containing ruthenium as a main constituting element andtitanium in an amount of 25 atom % as an adding element on a siliconoxide film at 900 K, followed by cooling to 300 K. The film thickness ofthe capacitor electrode film and the silicon oxide film was 3 nm. Asshown in FIG. 6, the atomic configuration of the capacitor electrodefilm is disturbed irregularly near the interface, but the upper layer isare ranged regularly. When the oxide film material having the perovskitecrystal structure is formed on the electrode film having such an atomicconfiguration, there is no problem.

When simulation was conducted by forming a capacitor electrode filmcontaining ruthenium as a main constituting element and zirconium in anamount of 5 atom % as an adding element on a silicon oxide film at 900K, followed by cooling to 300 K, the results are as shown in FIG. 7. Inthis case, each film thickness was made 3 nm. From FIG. 7, it is clearthat when zirconium is added, the atomic configuration of the capacitorelectrode film become irregular in the whole film, and formation of theperovskite crystal structure on the electrode film having such adisturbed atomic configuration becomes difficult.

Similarly, when simulation was conducted by forming a capacitorelectrode film containing ruthenium as a main constituting element andhafnium in an amount of 25 atom % on a silicon oxide film at 900 K,followed by cooling to 300 K, the atomic configuration of the electrodefilm was disturbed irregularly in the same manner as the case of usingzirconium as the adding element.

A reason for causing disturbance of atomic configuration of theelectrode film when zirconium or hafnium is used as the adding elementin the electrode film seems to be a large difference in the atomicradius of the main constituting element of electrode film and the atomicradius of the adding element. In fact, the difference between the atomicradius of ruthenium and the atomic radius of titanium is about 5%, whilethe difference between the atomic radius of zirconium or hafnium and theatomic radius of ruthenium is as large as about 19% or about 18%.

The present inventors have further studied based on the above facts andfound that when the difference between the atomic radius of mainconstituting element and that of the adding element is over 10%, thereeasily brings about in the electrode film disturbance of atomicconfiguration which damages the formation of perovskite crystalstructure of the oxide film material on the electrode film.

From the above-mentioned results of the study of the present inventors,the following things becomes clear. That is, among palladium, cobalt,nickel, titanium hafnium and zirconium which are effective for improvingthe adhesiveness, hafnium and zirconium cause undesirable disturbance ofatomic configuration in the capacitor electrode film. Therefore,palladium, cobalt, nickel and titanium are effective as the addingelement.

When the content of the adding element in the capacitor electrode filmbecomes excess, it is possible to bring about undesirable disturbance inthe atomic configuration. Therefore, molecular dynamic simulation forspecifying the content of adding element not disturbing the atomicconfiguration in the electrode film was conducted.

FIG. 6 shows the case of forming a capacitor electrode film containingruthenium as a main constituting element and titanium in an amount of 25atom % as the adding element on a silicon oxide film. As shown in FIG.6, the atomic configuration of capacitor electrode film near interfacedisturbs irregularly, while the upper layer is arranged regularly. Theformation of perovskite crystal structure of dielectric material on theelectrode film having such an atomic configuration has no problem asmentioned above.

In contrast, when a simulation is conducted by forming a capacitorelectrode film (film thickness 3 nm) containing ruthenium as a mainconstituting element and titanium in an amount of 26 atom % as addingelement on a silicon oxide film (film thickness 3 nm) at 900 K, followedby cooling to 300 K, the results are as shown in FIG. 8. As shown inFIG. 8, the atomic configuration of capacitor electrode film isirregular in whole film. Thus, it becomes difficult to form perovskitecrystal structure of oxide film material on the electrode film havingsuch an atomic configuration.

In the same manner as mentioned above, the simulation was conducted byusing palladium, cobalt or nickel as the adding element. As a result, itwas found that when the content of the adding element is 25 atom % orless, the perovskite crystal structure of oxide film material can beformed stably on the electrode film without producing undesirabledisturbance in crystal structure of atomic configuration in theelectrode film. Further, when a plurality of elements were contained inthe electrode film as adding elements, the same results were obtained.In addition, when rhodium, iridium, osmium and platinum were used inplace of ruthenium as the main constituting element, the same resultswere obtained. From the above results, it can be understood that thecontent of 25 atom % of adding element means a critical value.

In order to improve the adhesiveness of the capacitor electrode to thesilicon oxide film, there can be required the following factorsconsidering the above facts. First, as a factor for improving theadhesiveness, the bond energy between the adding element and silicon andthe content of adding element. As to the bond energy between the addingelement and silicon, it is required to be 2 times or more as large asthe bond energy between the main constituting element in the capacitorelectrode and silicon. On the other hand, the content of adding elementis required to be about 10 atom % or more.

Next, as a factor for not producing undesirable disturbance in thecrystal structure in the capacitor electrode film, there are the atomicradius of adding element and the content of adding element. The atomicradius of adding element is required to be not exceeding 10% in thedifference compared with the atomic radius of the main constitutingelement of the capacitor electrode film. That is, the adding element isrequired to have the bond energy to silicon of 2 times or more as largeas the bond energy between the main constituting element and silicon,and to have the atomic radius of 10% or less in difference compared withthe atomic radius of the main constituting element. As the elementssatisfying the above factors, there can be recited palladium, nickel,cobalt and titanium. The adding amount of these adding elements is about10 atom % to about 25 atom %.

In the above, explanation was made as to the case of using at least oneelement selected from rhodium, ruthenium, iridium, osmium and platinumas the main constituting element for forming the capacitor electrode,but according to the stud of the present inventors, the same results asmentioned above were also obtained when at least one electroconductivematerial selected from ruthenium oxide and iridium oxide was used as themain constituting material.

Next, steps for producing main part of DRAM shown in FIG. 1 areexplained by using FIG. 9 to FIG. 12.

As shown in FIG. 9, on a silicon substrate 1, an element separation film4, a transistor 2, an insulating film 9, a plug 10, a plug 13, a bitline 11, an insulating film 12 a, and an electroconductive film 14 areformed by a conventional process, followed by flattening of surfaces ofthe insulating film 12 a and electroconductive film 14 by. a chemicalmechanical polishing (CMP) method, etc. On the surfaces of theinsulating film 12 a and electroconductive film 14, SiO₂ or the likefilm is deposited by a CVD method or the like, and trenches for forminga capacitive cell are formed by etching or the like to form aninsulating film 12 b (FIG. 10). Subsequently, on the surfaces of theinsulating film 12 a, the electroconductive film 14 and the insulatingfilm 12 b, a film 15 a for a first capacitor electrode film 15 is formedusing ruthenium or ruthenium alloy containing titanium in aconcentration between 10 atom % and 25 atom % as the adding element by asputtering method, a CVD method, a plating method, a vapor depositionmethod, or the like (FIG. 11). In this case, the sputtering method hasan advantage of showing better adhesiveness of the formed film 15 a tothe insulating films. On the other hand, the CVD method has an advantageof giving more uniform film thickness of the formed film 15 a at theside walls and the bottom of the trenches for forming the capacitor cell(the portions finally forming the first capacitor electrode film 15). Asthe adding element for the film 15 a, there can be used palladium,nickel, or cobalt in place of titanium. As the main constituting elementfor the film 15 a, there can be used rhodium, iridium, osmium orplatinum in place of ruthenium or ruthenium alloy. Further, eitherruthenium oxide or iridium oxide can also be used.

Then, extra portions formed except for the trenches are removed from thefilm 15 a by, e.g. a CMP method, to form an under electrode film (firstcapacitor electrode film 15) (FIG. 12). In this step, when theadhesiveness of the film 15 a to the insulating film 12 b is low, thereis a possibility of causing a trouble of peeling of the film 15 a fromthe insulating film 12 b. But according to the present invention, sinceas the adding element there is contained titanium in a concentration of10 to 25 atom %, or palladium, nickel or cobalt in place of titanium ina concentration of 10 to 25 atom %, the adhesiveness between the film 15a and the insulating film 12 b is improved remarkably. Thus, in the stepof removing partly the film 15 a by the CMP method or the like, it ispossible to effectively prevent a problem of peeling of the film 15 a(the first capacitor electrode film 15) which is to be retained from theinsulating film 12 b. Further, in the subsequent steps, the effect ofthe present invention of having excellent adhesiveness between the firstcapacitor electrode film 15 and the insulating film 12 b can functioneffectively.

Subsequently, on the first capacitor electrode film 15 and theinsulating film 12 b for interlaminar insulation, a capacitor dielectricfilm (oxide film) 16 is formed by using a dielectric material such asbarium strontium titanate (Ba, Sr) TiO₃: BST), zirconium lead titanate(Pb(Zr, Ti)O₃: PZT), etc. by a sputtering method, a CVD method, or laserabrasion method. Then, on the oxide film 16, an upper electrode film(second capacitor electrode film 17) is formed by using ruthenium orruthenium alloy containing titanium as adding element in a concentrationof 10 to 25 atom % by a sputtering method, a CVD method, or a vapordeposition method. As to the second capacitor electrode film 17, therecan be used as the adding element palladium, nickel or cobalt in placeof titanium. As the main constituting element or main constitutingmaterial, there can be used rhodium, iridium, osmium, or platinum inplace of ruthenium or ruthenium alloy, as well as ruthenium oxide oriridium oxide. Finally, on the upper electrode film, an insulating filmsuch as SiO₂ or the like film is deposited to obtain the structure ofmain part of DRAM as shown in FIG. 1. After this, the steps arecompleted in the same manner as conventional steps for producing DRAM.

EXAMPLE 2

FIG. 13 is a cross-sectional view showing the structure of main part ofDRAM, a semiconductor device. In FIG. 13, the same numerals as in FIG. 1have the same meaning. The semiconductor device of this Example has aMOS type transistor 2 formed in the active region of the main surface ofthe silicon substrate 1 and an information storage capacitor 3 on theupper portion thereof.

The MOS transistor 2 for memory cell selection comprises a gateelectrode 5, a gate insulating film 6 and diffusion layers 7 and 8. Thegate insulating film 6 is made from, for example, a silicon oxide film,a silicon nitride film, a ferroelectric film, or a laminated structurethereof. The gate electrode 5 is made from, for example, apolycrystalline silicon film, a metal thin film, a metal silicide film,or a laminated structure thereof. On the upper portion and side portionsof the gate electrode 5, an insulation film 9 made from, for example, asilicon oxide film is formed. One of the diffusion layer 7 of the MOStransistor 2 is connected to a bit line 11 via a plug 10. The upperportion of the MOS transistor 2 is covered by an insulating film 12 afor interlaminar insulation made from, for example, a BPSG film, a SOGfilm, or a silicon oxide film or a silicon nitride film formed by a CVDmethod or a sputtering method.

On the upper portion of the insulating film 12 a covering the MOStransistor 2, an information storage capacitor 3 is formed. Theinformation storage capacitor 3 is connected to another diffusion layer8 via a plug 13 made of, for example, polycrystalline silicon. Theinformation storage capacitor 3 comprises an electroconductive barrierfilm 14, an insulating film 20 for interlaminar insulation made of, forexample, silicon oxide film, a first capacitor electrode 21, an oxidefilm 22 for dielectric having high dielectric constant orferroelectricity and a second capacitor electrode 23 in a laminatedstructure, the upper portion of which is covered with an insulating film24 made from a silicon oxide film for interlaminar insulation.

In this Example, the first capacitor electrode 21 or the secondcapacitor electrode 23 or both of them is composed of the followingcomposition. That is, at least one of the first capacitor electrode andthe second capacitor electrode is made of at least one element selectedfrom the group consisting of rhodium, ruthenium, iridium, osmium andplatinum as the main constituting element, or ruthenium oxide or iridiumoxide as the main constituting material, and at least one elementselected from the group consisting of palladium, nickel, cobalt andtitanium as the adding element in a concentration of 10 to 25 atom %.

A process for producing the main portions of DRAM shown in FIG. 13 isexplained referring to FIGS. 14 to 17. First, as shown in FIG. 14, on asilicon substrate 1, an element separation film 4, a transistor 2, aninsulating film 9, a plug 10, a plug 13, a bit line 11, an insulatingfilm 12 a, and an electro-conductive film 14 are formed by aconventional method, followed by flattening of the surfaces of theinsulating film 12 a and the electroconductive film 14. Then, on thesurfaces of the insulating film 12 a and the electroconductive film 14,an insulating film 20 is formed by using SiN₄, etc. by a CVD method orthe like. Further, an insulating film 25 is deposited thereon by usingSiO₂ or the like (FIG. 14). Then, a trench 26 for forming a capacitivecell is formed by etching the insulating film 20 and the insulating film25 (FIG. 15). Then, on the surfaces of the trench 26 and the insulatingfilm 25, a film of ruthenium or ruthenium alloy containing as the addingelement titanium in a concentration of 10 to 25 atom % is formed by asputtering method, a CVD method or a vapor deposition method. Here, asthe adding element to the above film, there can be used palladium,nickel or cobalt in place of titanium. Further, as the main constitutingelement, there can be used rhodium, iridium, osmium or platinum in placeof ruthenium or ruthenium alloy, as well as ruthenium oxide or iridiumoxide.

Then, extra film formed on portions except for the trench 26 is removedby, for example, CMP or the like to form a lower electrode film (firstcapacitive electrode 21) (FIG. 16). In this step, when the adhesivenessbetween the film for lower electrode and the insulating film 25 is low,there is a possibility of causing a trouble of peeling of this film fromthe insulating film 25. But in the present invention, since the film forlower electrode contains titanium or the like in a concentration of 10to 25 atom %, the adhesiveness between this film and the insulating film25 is improved remarkably. Therefore, the peeling of the lower electrodefilm, which should be retained in the partial removing step of the filmfor lower electrode by a CMP method or the like, from the insulatingfilm 25 can effectively be prevented.

Subsequently, the insulating film 25 is removed by etching or the liketo expose the first capacitor electrode 21 (FIG. 17). On the exposedsurface of first capacitor electrode 21, a capacitor dielectric film(oxide film 22) is formed by using a dielectric material such as BST,PZT, or the like by a sputtering method, a CVD method, or a laserabrasion method. Then, on the capacitor dielectric film, an upperelectrode film (second capacitor electrode film 23) is formed by usingruthenium or ruthenium alloy containing titanium as the adding elementin a concentration of 10 to 25 atom % by a sputtering method, a CVDmethod, or a vapor deposition method. As the second capacitor electrodefilm 23, there can also be used as the adding element palladium, nickel,or cobalt in place of titanium. As the main constituting element or mainconstituting material, there can be used rhodium, iridium, osmium, orplatinum in place of ruthenium or ruthenium alloy, as well as rutheniumoxide or iridium oxide. Finally, on the upper electrode film, aninsulating film such as SiO₂, or the like is deposited to give thestructure of main part of DRAM as shown in FIG. 13. Thereafter,conventional steps are carried out to produce DRAM completely.

The finally formed first capacitor electrode 21 in the semiconductordevice (DRAM) of this Example has a small area contacting with theinterlaminar insulating film (insulating film 20) as shown in FIG. 13.On the other hand, the first capacitor electrode 21 contacts with theinsulating film 25 in a broader area during the production steps asshown in FIG. 16. Thus, adhesiveness between the insulating film 25 andthe first capacitor electrode 21 becomes important. From this reason, toform the first capacitor electrode 21 by using the above-mentionedmaterial is effective for enhancing the adhesiveness between the firstcapacitor electrode 21 and the insulating film 25.

In the above-mentioned Examples 1 and 2, palladium, nickel, cobalt andtitanium were treated equally as the adding element. But, according tothe study of the present inventors, it is found that titanium and nickelare particularly excellent. That is, in order to improve theadhesiveness, titanium is the most effective, and when heat treatment isconducted in an oxygen atmosphere, the most excellent adding element inelectrical stability is nickel. From these results, it is morepreferable to use titanium or nickel as the adding element.

EXAMPLE 3

FIG. 18 is a cross-sectional view of the structure of main part of thesemiconductor device (DRAM) of Example 3. In FIG. 18, the same numeralsas used in FIG. 1 have the same meaning as in FIG. 1. A major differencebetween the semiconductor device of Example 3 and that of Example 1 isthe presence of a sticking layer 26 between the insulating film 12 b andthe first capacitor electrode 15. The sticking layer 26 is anelectroconductive film containing one element selected from palladium,nickel, cobalt and titanium as the main constituting element. Sincethese elements have larger bond energy for silicon, the sticking layer26 shows high adhesiveness to the insulating film 12 b. Therefore, inthe structure having the sticking layer 26, the first capacitorelectrode 15 not always requires an adding element.

As a result, in this Example, the first capacitor electrode 15 can beformed from (i) only one element selected from the group consisting ofrhodium, ruthenium, iridium, osmium, and platinum, (ii) a mainconstituting element being selected from these elements mentioned in (i)and an adding element in an amount smaller than that in Example 1, (iii)only one material selected from ruthenium oxide and iridium oxide, and(iv) a main constituting element being selected from these materialsmentioned in (iii) and an adding element in an amount smaller than thatin Example 1. By taking such a structure, not only the peeling problemof the first capacitor electrode 15 can effectively be avoided by thepresence of the sticking layer 26, but also the disturbance of atomicrearrangement in the first capacitor electrode 15 can be reducedremarkably, resulting in more enhancing the stability of the oxide film16.

In this Example, the electroconductive film (sticking layer 26) isformed only as to the first capacitor electrode 15. But, it is alsopossible to form the electroconductive film as to the second capacitorelectrode 17 between the insulating film 18 and the second capacitorelectrode 17. The adhesiveness to the insulating film is particularlyimportant in the case of the first capacitor electrode 15. Thus, theembodiment of providing the electroconductive film only for the firstcapacitor electrode 15 is explained as a typical example.

EXAMPLE 4

FIG. 19 is a cross-sectional view of a structure of main part of asemiconductor device (DRAM). of Example 4. In FIG. 19, the same numeralsas used in FIG. 1 have the same meaning as in FIG. 1. A major differencebetween the semiconductor device of Example 4 and that of Example 1 isthat the first capacitor electrode comprises two electrode films 27 and28. The electrode film 27 at a side contacting with the insulating film12 b is made of one element selected from the group consisting ofrhodium, ruthenium, iridium, osmium and platinum as a main constitutingelement or one material selected from the group consisting of rutheniumoxide and iridium oxide as a main constituting material together withone element selected from the group consisting of palladium, nickel,cobalt and titanium as an adding element in a concentration of 10 to 25atom % in order to enhance the adhesiveness to the insulating film 12 b.

On the other hand, the electrode film 28 at a side contacting with theoxide film 16 does not always contain an adding element due to notcontacting with the insulating film 12 b. Thus, the electrode film 28 ismade from (i) only one element selected from the group consisting ofrhodium, ruthenium, iridium, osmium, and platinum, (ii) a mainconstituting element being selected from these elements mentioned in (i)and an adding element in an amount smaller than that in the electrodefilm 27, (iii) only one material selected from ruthenium oxide andiridium oxide, and (iv) a main constituting element being selected fromthese materials mentioned in (iii) and an adding element in an amountsmaller than that in the electrode film 27.

By taking such a structure, the same effects as Example 3 are obtained.That is, the adhesiveness to the insulating film 12 b is sufficientlysecured by the electrode film 27 on one hand, and the stability of theoxide film 16 can further be enhanced by making the disturbance ofatomic rearrangement in the electrode film 28 lesser.

As to the structure in Example 4, it is possible to make the number oflayers of the first capacitor electrode three or more. For example,between the electrode film 28 and the oxide film 16, it is possible tointerpose another layer more excellent in control of crystal structurein the oxide film 16. Further, in this example, only the first capacitorelectrode is made in a multilayer structure, but it is also possible tomake the second capacitor electrode a multilayer structure.

As explained above, according to the present invention, a problem ofadhesiveness between the capacitor electrode film and the insulatingfilm caused by higher integration of semiconductor devices equipped withinformation storage capacitor can be solved and the semiconductordevices with higher reliability can be provided.

What is claimed is:
 1. A semiconductor device equipped with a capacitorfor storing information comprising a substrate, a first capacitorelectrode formed on the substrate, an oxide film formed in contact withthe first capacitor electrode, a second capacitor electrode formed incontact with the oxide film, and an insulating film containing siliconas a main constituting element and formed in contact with the firstcapacitor electrode or the second capacitor electrode, said firstcapacitor electrode or said second capacitor electrode which is incontact with the insulating film containing as a main constitutingelement at least one element selected from the group consisting ofrhodium, ruthenium, iridium, osmium, and platinum, and as an addingelement at least one element selected from the group consisting ofnickel and titanium in an amount of 10 atom % or more.
 2. Asemiconductor device equipped with a capacitor for storing informationcomprising a substrate, a first capacitor electrode formed on thesubstrate, an oxide film formed in contact with the first capacitorelectrode, a second capacitor electrode formed in contact with the oxidefilm, and an insulating film containing silicon as a main constitutingelement and formed in contact with the first capacitor electrode or thesecond capacitor electrode, said first capacitor electrode or saidsecond capacitor electrode which is in contact with the insulating filmcontaining as a main constituting element ruthenium, and as an addingelement at least one element selected from the group consisting ofnickel and titanium in an amount of 10 atom % or more.
 3. Asemiconductor device equipped with a capacitor for storing informationcomprising a substrate, a first capacitor electrode formed on thesubstrate, an oxide film formed in contact with the first capacitorelectrode, a second capacitor electrode formed in contact with the oxidefilm, and an insulating film containing silicon as a main constitutingelement and formed in contact with the first capacitor electrode or thesecond capacitor electrode, said first capacitor electrode or saidsecond capacitor electrode which is in contact with the insulating filmcontaining as a main constituting element ruthenium, and as an addingelement titanium in an amount of 10 atom % or more.
 4. A semiconductordevice equipped with a capacitor for storing information comprising asubstrate, a first capacitor electrode formed on the substrate, an oxidefilm formed in contact with the first capacitor electrode, a secondcapacitor electrode formed in contact with the oxide film, and aninsulating film containing silicon as a main constituting element andformed in contact with the first capacitor electrode or the secondcapacitor electrode, said first capacitor electrode or said secondcapacitor electrode which is in contact with the insulating filmcontaining as a main constituting element ruthenium, and as an addingelement nickel.
 5. A semiconductor device equipped with a capacitor forstoring information comprising a substrate, a first capacitor electrodeformed on the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode or the second capacitor electrode, said first capacitorelectrode or said second capacitor electrode which is in contact withthe insulating film containing as a main constituting material at leastone material selected from ruthenium oxide and iridium oxide, and as anadding element at least one element selected from the group consistingof palladium, nickel, cobalt, and titanium.
 6. A semiconductor deviceaccording to any one of claims 1 to 5, wherein the adding element iscontained in a concentration of 10 to 25 atom %.
 7. A process forproducing a semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film for a dielectric formed in contact withthe first capacitor electrode, a second capacitor electrode formed incontact with the oxide film, and an insulating film containing siliconas a main constituting element and formed in contact with the firstcapacitor electrode or the second capacitor electrode, which comprisesforming the first capacitor electrode or the second capacitor electrodewhich is in contact with the insulating film by using (a) at least oneelement selected from the group consisting of rhodium, ruthenium,iridium, osmium and platinum as a main constituting element and at leastone element selected from the group consisting of nickel and titanium asan adding element in an amount of 10 atom % or more, or (b) at least onematerial selected from the group consisting of ruthenium oxide andiridium oxide as a main constituting material, and at least one elementselected from the group consisting of nickel and titanium as an addingelement in an amount of 10 atom % or more.
 8. A semiconductor deviceequipped with a capacitor for storing information comprising: a firstcapacitor electrode; a second capacitor electrode; an oxide film; and aninsulating film, said insulating film being formed outside of said firstcapacitor electrode or said second capacitor electrode, wherein saidfirst capacitor electrode or said second capacitor electrode contain asa main constituting element at least one element selected from the groupconsisting of rhodium, ruthenium, iridium, osmium, and platinum, and,near the boundary of said insulating film, said first capacitorelectrode or said second capacitor electrode includes a regioncontaining an element selected from the group consisting of palladium,nickel, cobalt, and titanium in a concentration of more than about 15atom %.
 9. A semiconductor device equipped with a capacitor for storinginformation comprising a substrate, a first capacitor electrode formedon the substrate, an oxide film formed in contact with the firstcapacitor electrode, a second capacitor electrode formed in contact withthe oxide film, and an insulating film containing silicon as a mainconstituting element and formed in contact with the first capacitorelectrode or the second capacitor electrode, said first capacitorelectrode or said second capacitor electrode which is in contact withthe insulating film containing as a main constituting element at leastone element selected from the group consisting of rhodium, ruthenium,iridium, osmium, and platinum, and means for enhancing adhesiveness ofsaid first or said second capacitor electrode to said insulating film toprevent peeling comprising providing as an adding element to said firstor second capacitor electrode at least one element selected from thegroup consisting of nickel and titanium.
 10. A semiconductor deviceaccording to claim 9, wherein the adding element is contained in aconcentration of 10 atom % or more.